In general, a vacuum window refers to a kind of glass window in which a vacuum is formed between upper and lower plates thereof for blocking noise and vibrations and improving thermal insulation by blocking thermal energy transferred from the outside.
In the related art, vacuum windows are manufactured by applying a frit (frit seal) to the edges of a glass plate including a pair of upper and lower plates, heat treating the glass plate, cooling the glass plate at room temperature, and creating a vacuum between the upper and lower plates.
Particularly, an exhaust hole is formed in the lower plate, and a tip in the form of a short pipe is attached to the exhaust hole. Then, a vacuum hose is connected to the tip, and air is discharged from between the upper and lower plates to create a vacuum. Thereafter, the vacuum hose is removed, and the tip is welded to seal the vacuum.
However, vacuum windows manufacturing according to the above-described method of the related art have many problems such as forming of vacuum windows having uneven surfaces due to tips fused to lower plates and protruding therefrom, low functionality caused by a low degree of vacuum created using the vacuum hose, product damage caused by protruding tips vulnerable to impacts.
Particularly, since pallets for transferring large vacuum windows under high-temperature, high-vacuum-degree conditions have not yet been developed for the vacuum window manufacturing method, a series of processes has to be manually performed. That is, process automation and automatic line production are impossible. As a result, productivity is very low.